CLDN1 and escherichia coli infection: In the present study, we found that L. fermentum MC018 supplementation not only alleviated intestinal injury of geese with E. coli infection and elevated the levels of Claudin-1, Occludin, ZO-1, and DAO, but also reduced the diarrhea rate and E. coli count and increased LAB count in both ileum and rectum.